Multiple compressor truck refrigeration unit



Aug. 8, 1950 A. R. CLARK 2 MULTIPLE COMPRESSOR TRUCK REFRIGERATION. UNIT Filed Dec. 4, 1948 zmn (jam j? mm;

Patcntel Aug. 8, 1950 MULTIPLE COMPRESSOR TRUCK REFRIGERATION UNIT Adna R. Clark, Evansville, Ind., assizor to Internationai Harvester Company, a co'portion of New Jersey Application December 4, 1948, Serial No. 83,494

2 Clains.

This invention relates to refrigeration apparatus, but more specifically it is concerned with automotive truck-trailer rei'rigeration apparatus and the means for maintaining low temperatures in refrigeration units of this character.

Ordinarily in units of this character the temperature of the reirigerated compartment is maintained Somewhere between 35 and 45 degrees F. and, usually, the system is designed according to the requirements necessary to maintain such temperatures. However, there are frequently occasions when it is necessary to provide much lower temperatures. usually in the zero degree F. range, and the conventional system is not designed to maintain such temperatures without dangerous overloading of the refrigeration apparatus. Although it is, of course, possible to design and provide the refrigeration apparatus necessary to maintain these low temperatures, it is not economical to do so; thus the conventional truck-trailer refrigeration unit is not suitable when products requiring low temperatures must be transported. Furthermore, the installation of refrigeration apparatus in automotive trucks and trailers has met with a certain amount of opposition from the motor transportation industry because such installations invariably introduce additional problems without always providing adequate or completely compensatory benefits. Economy dictates that trucks and trailers be operated at all times so as to permit haulage of the maximum cargo at minimum costs; hence any additional equipment. such as refrigeration apparatus carried therein, not only adds to the weight that must be transported and frequently reduces available cargo space, but also minimizes potential profits. Because of such limitations, truck-trailer refrigeration apparatus must be designed so as to have a minimum of weight and yet be capable of operation at maximum emciency under extremely variable load conditions.

since it would be inadvlsable from a technical as weil as economic viewpoint to attempt to provide refrigeration apparatus with sufllcient flexibility to be able to maintain the customary refrigeration temperatures and yet be suitable for maintaining the infrequently required low temperatures, the present invention is concerned with a meansfor providing low temperatures, when required, in a conventional system without unduly adding to the no-pay load or reducing the available cargo carrying space.

It is a principal object of this invention, therefore, to provide a novel and economical means i'or increasing or boosting the refrlgeration capacity oi' automotive truck-trailer retrigeration apparatus.

Another important object is to provide a trucktrailer reirigeration apparatus with means tor introducing auxillary booster rei'rigeration capacity into the system.

A further object is to provide tor the introductlon o! an auxiliary refrigerant compressor in truck-trailer refrigeration apparatus so that the capacity oi said compressor may be used to supplement the capacity of the refrigeration system in maintaining low temperatures.

A still further object is to provide automotive truck-trailer reirigeration apparatus having a primary compressor and a separate auxiliary compressor that may be operatively coupled into the refrigeration system when low temperatures are required in the retrigerated compartment.

A yet still further object is to provide automotive truck-trailer refrigeration apparatus having a primary compressor and a separate auxiliary compressor that may be automatically coupled into or out oi parallel operation with the primary compressor when low temperatures are required to be maintained in the refrigerated compartment. v

The foregoing and other objects and features of the inventlon will become apparent as the disclosure is more fully made in the following detailed description ot a preferred embodiment of the invention as illustrated in the accompanying sheet oi' drawin` in which the figure is a schematic layout of an automotive truck-trailer retrigeration unit which has been provided with a booster or auxiliary compressor in accordance with the teachings oi' this invention.

Referring to the drawing. it will be noted that a conventional truck-trailer refrigeration unit has been fllustrated in diagrammatic form and further shown as positioned with a portion thereof projecting into a refrigerated compart-- ment, while the remainder is exposed to the outside atmosphere. In the drawing. a driving motor. usually an internal combustion engine, is indicated generally by the numeral l and may be provided with a starter motor 2 and its associated Starter mechanism 3, and a generator 4 operatively coupled by a driving belt 5 to a tan 6 which. in turn, is driven directly by the engine I. A storage batte'y 'I may be used to provide the necessary source oi' electrlcal energy to operate said engine. The engine and its asso' ciated components may be flxedly Secured. as by a plurality of transverse members such as the one indicated by the numeral 8, to longitudinally extending side rails S and o of a frame structure indicated generally by the numeral 11. Since the details of this !rame structure are not important to the teachings of this invention, further description thereot appears unnecessary. Suflice it to say, however, that in a unit of this character the side rails S and o are usually aiiixed, by some suitable means such as the angle members |2 and !3, to the outside of the wall Il, which, in this case, represents a. portion of an insulated wall that encloses a refrigerated compartment IS.

A drive shaft IC, which may be operatively connected by any suitable means with the drive shaft of the engine, extends through the wall Il and into the refrigerated compartment li where it has aflixed thereabout a fan l`l, a pulley 18 and a clutch pulley !9. A refrigerant compressor 20, which may be aflixed by suitable means to the portion of the frame II that extends into the refrigerated compartment, is connected by a driving belt 2| with pulley ll and drive shaft IS, while a second compressor 22 is likewise connected through a driving belt 23 to clutch pulley I! and said drive shaft IS. It will be understood that suitable means will likewise be provided for flxedly supporting the compressor 22 on the frame structure.

A condenser, indicated generally by the numeral 24, may be mounted by suitable means on the rame ll, but preferably on the outside ends of the side raiis 9 and ll, while an evaporator, indicated gperally by the numeral 25, may be similarly mounted on the opposite ends of said side rails disposed within the refrigerated compartment !5. A conduit 26 connects the discharge outlet of the compressor 2! with the condenser 24 and a conduit 21 connects the suction side of said compressor with the evaporator 25, while a conduit 28 provides a connection between said condenser and evaporator. Additional conduit lines 29 and 30 inter-connect, the two compressors 20 and 22.

The clutch pulley IS, in accordance with the teachings of this invention, is adapted for driving engagement with the drive shait II through an automatically controlled clutch Il. which may be engaged or disengaged according to predetermined temperature conditions within the refrigerated compartment IS. A clutch of this character may be electrically operated and actuated by the electrical system of the engine, or it may be mechanically operated through appropriate mechanism (not shown). In either case. its operation would be controlled by thermostatic control means responsive to pre-selected temperatures in the refrigerated compartment. Since no claim is made to the specific type of control for such a clutch mechanism further details thereof are not included herein. It will be understood, however; that any one of many such commercial products as are now available on the market may be suitably employed for eflecting the control desired without in any way limiting the scope of the present invention.

In operation a refrigeration unit of this character functions, under normal Operating conditions, in accordance with well-known principles. Refrigerant compressed in the compressor 2! is discharged through conduit 26 into condenser 24 where it is cooled and then directed, by way oi conduit 28, into the evaporator 25. Upon leaving the evaporator the heated rerigerant returns, by way of conduit 21, to the suction inlet of the compressor 20 to complete its normal cycle. Con- 4 ventional thermostatic control means, or thelike. may be provided to maintain the refrigerated compartment at the desired predetermined temperature.

Now, as heretofore discussed, when a temperature lower than that for which the system is ordinarily adapted is desired, the refrigeration unit operates in efiecting the initial pull down of the temperature in the refrlgerated compartment, and when this temperature reaches a predetermined value the thermostatic control provided for the auxiliary compressor operates to actively engage the clutch :I and drivingly connect the drive shait I! with said auxiliary compressor 22 whereupon both compressors Operating together further lower the temperature of the compartment to that ultimately desired. When the auxiliary compressor 22 is set into operation it immediately supplements the flow of refrigerant from the primary compressor 20, through the condensor 24 and evaporator 25, and, Operating in parallel with said primary compressor, functions to provide the additional piston displacement necessary to eflectuate and maintain the desired lower temperature in the refrigerated compartment. The engagement and disengagement of the auxiliary compressor 22 through the clutch 3l maybe effected by means of a conventional mechanical mechanism or by electrical means as heretofore explained. Upon completion of the demand for the lower temperature in the refrigerated compartment the auxiliary thermostatic control by which such temperature is governed may be disengaged, whereupon the refrigeration unit will return to normal operation and thereafter continue to maintain the customary temperature therein.

It will be apparent from the above description that the present invention substantially extends the usefulness of conventional automotive trucktrailer refrigeration apparatus and envisages the adaptation thereof to such a system with a minimum of alteration and the addition of relatively few parts. The proposed invention, furthermore, is readily adaptable to such systems without necessitating any costly redesign of apparatus, and is relatively inexpensive to install.

It should now be apparent that a novel lowtemperature truck-trailer refrigeration unit has been shown and described, and it is to be understood that changes may be made in the construction without departing from the spirit of the invention or the scope thereof as deflned in the appended claims.

What is claimed is:

1. In refrigeration' apparatus of the class described, in combination: a compressor, a condenser, and an evaporator connected in a closed circuit; engine means for driving said compressor; said engine having a drive shaft extending from opposite ends thereof with one end of said shaft terminating proximate the condenser and being provided with a fan for circulating air over the condenser while the opposite end of said shaft terminates proximate the evaporator and is provided with a fan for circulating air over said evaporator; said shaft having driving means securely positioned thereon, intermediate the evaporator fan and the engine, that is adapted for engaging said compressor in driving relation with said engine; means including an auxiliary compressor adapted to operate in parallel with the compressor of the refrigeration apparatus for increasing the refrigeration capacity thereof and having said engine shaft further provided with clutch means positioned thereon intermediate said evaporator fan and said engine for engaging and disengaging said uxiliary compressor in driving relation with said engine.

2. In refrigeration apparatus of the class described, in combination: a compressox a condenser, and an evaporator connected in a closed circuit; an internal combustion engine; said engine having a drive shaft extending from opposite ends thereof with one end of said shaft terminating proximate the condenser and being provided with a. fan for circulating air over the condenser while the o pposite end of said shaft terminates proxinate the evaporator and is provided with a fan for circulating air over said evaporator; said shaft having driving means securely positioned thereon intermediate the evaporator fan and the engine that is adapted for engaging said compressor in driving relation with said engine; said compressor being spaced from and positioned to one side of said shaft; means including an auxiliary compressor adapted to operate in parallel with the compressor of the refrigeration apparatus for facilitating the produc- REFERENCES CITED The following references are of record in the file of this patent:

'UNITED STATES PA'I'ENTS Number Name Date 1,943,963 Hulse Jan. 16, 1934 2,157,329 Fillo May 9, 1939 2,193,837 Winther et al Mar. 19, 1940 2,231,069 Harris Feb. 11, 1941 2,274,774 Chambers Mar. 3, 1942 2,281,626 Smith May 5, 1942 

